Such vehicles are described for instance in U.S. Pat. Nos. 3.601.213 and 3.781.031 by the same inventor Pierre Patin. The rear wheelset is constituted of two wheels of which the axles are perpendicular to the median plane of the primary part and are preferably mounted so as to incline with the primary part, so that the vehicle which is stable at standstill, due to its three wheels, is used when rolling like a two wheel vehicle able to incline towards inner side of a curve so as to compensate the centrifugal force: in that case, the median plane of the primary part passing by the forewheel and the center of the rear wheelset coincide with the median plane of the secondary part, passing by the suspension axis and the center of gravity, and is inclined in the direction of the apparent vertical, that is to say the resultant of gravity force and centrifugal force.
For a good stability, it is preferable that both wheels of the rear wheelset incline like the forewheel with the primary part, remaining parallel to the median plane, and, in that aim, the rear wheelset is advantageously mounted upon the primary part using a deformable parallelogram comprising two lateral vertical rods parallel to the median plane of the primary part, the ends of which are hinged with two parallel equalizers, articulated upon the primary part, respectively around two axis placed upon one another in the median plane and parallel to the ground, the axles of both rear wheels being solid respectively with said vertical rods perpendicularly to the median plane.
In French Pat. No. 2.600.612 filed June 27, 1986 by same inventor, it has been described a device allowing to increase the stability of the vehicle by lifting the center of gravity in relation with the ground when the vehicle tends to incline, what increases the potential energy and consequently the stability of the vehicle, such an energy increase being impossible without a supply of energy from outside.
In that aim, the device described in French Pat. No. 2.600.612 comprises a rotation-multiplying system which allows, when the primary part inclines by an angle A in relation with the vertical, to induce a rotation of the secondary part by an angle B greater than A, what induces a lifting of the center of gravity of the secondary part in relation with the ground.
According to one of the embodiments described in patent 2.600.612, the rotation-multiplying system comprises a control cross-bar rotatably solid with secondary part and extended transversely towards each side of the median plane of said secondary part, and two transversal arms mounted respectively upon both lateral vertical rods of the parallelogram, transverse to said rods, each of said arms finding a support respectively upon the end of the control cross-bar opposed to the corresponding lateral rod thanks to a sliding linkage.
The working principle of such a system is described accurately in French Pat. No. 2.600.612 and does not need further development. As a rule, when the primary part rotates in relation with the ground, the secondary part is lifted thanks to the rotation of a member such as a rotating suspension arm articulated upon the primary part and bearing said secondary part, that rotation being multiple of the rotation of the median plane of the primary part in relation with the ground. In the overcited patent were described various means allowing that rotation linkage to be effective only when needed, specially at standstill, thanks to a clutching system which can be controlled by the driver and / or by the speed and / or by the inclination in relation with the vertical when at standstill and with the apparent vertical--that is to say the resultant of gravity force and of centrifugal force--when rolling.
The invention relates to a new stabilization device based on the same principle and using as a rule the same features as described in French Pat. No. 2.600.612, the new device being more simple and cheaper than the previous features and increasing reliability and safety of the vehicle.
The invention therefore is tied to the stabilization device previously described in which the rotation-multiplying system comprises a cross-bar solid in rotation with the secondary part and two transversal arms mounted respectively upon both lateral vertical rods of the parallelogram, transversely to said lateral rods and each finding a support, respectively, upon the end of the control cross-bar opposed to the corresponding lateral rod.
According to the invention, each transversal arm may move parallel to itself along the corresponding lateral rod when the median planes of both primary and secondary parts coincide between themselves and with the direction of the apparent vertical, but, if the center of gravity of secondary part moves out of the median plane by the action of gravity and / or external forces, at least one of both transversal arms is made solid with the corresponding lateral rod so as to make effective the rotation-multiplying system in the direction where it induces a lifting of the center of gravity of the secondary part by rotation of said secondary part in relation with primary part, said rotation producing a righting torque which brings back median planes of both primary and secondary parts in the same direction, which is the direction of the apparent vertical.
In that aim, according to the invention, each transversal arm is linked to the corresponding lateral rod through a sliding linkage which allows the movement of the arm along the lateral rod, that arm remaining perpendicular to said rod, said linkage comprising selective means to control locking and unlocking of said arm upon said rod, in relation with the orientation of the median planes of both primary and secondary parts in relation with the apparent vertical.
In a first embodiment of the invention, the sliding linkage between each transversal arm and the corresponding lateral rod comprises four shoes disposed in two pairs on each side, respectively inner side and outer side of the rod, and at two different levels, respectively upper level and lower level, each rod being able to slide with low friction between the corresponding shoes when both transversal arms are in line in middle position with the cross-bar, said shoes being able to be applied upon the opposite sides of the rod, one on each side at different levels, so as to make solid by friction the arm with the corresponding rod when said arm is discarded from its position by the cross-bar as the result of a movement of the centre of gravity of the secondary part in relation with the median plane of the primary part.
In another embodiment, each sliding linkage between a transversal and the corresponding lateral rod comprises a first pair of rollers mounted upon the arm and rotatable around axles parallel to the suspension axis of the secondary part, placed respectively on each side of the lateral rod and at two different levels, the upper roller resting upon the inner side of the rod and the lower roller upon the outer side of the rod, each roller being solid with a free-wheel or other equivalent means allowing its rotation only in the direction permitting to the arm to slide towards the lower part of the rod, so that, in the case when the action of the cross-bar tends to lift the arm, both rollers pushed respectively upon each side of the rod are locked in rotation and, thanks to their friction upon the rod, make the arm solid with said rod and put in action the rotation-multiplying system.
In such case, the linkage of the cross-bar with the parallelogram is realized, according to the direction of inclination of the vehicle by the arm which tends to slide towards the higher part of its rod, both arms resting respectively, in the opposite direction, upon two elastic supports solid with primary part.
But it is also possible to use both arms to control the rotation-multiplying system, each sliding linkage comprising then a second pair of rollers placed respectively at the other level and on the opposite side in respect to the rollers of the first pair, each roller being solid with a freewheel allowing the rotation of the second pair in the direction where the arm is lifted along the corresponding rod and locking that rotation in the opposite direction so as to make solid, in that case, the arm with the rod.
In a still more perfectionate embodiment, each transversal arm is fitted with a servo-mechanism controlling a movement of the arm along the rod, allowing to the primary part to follow an inclination given by the driver to the secondary part. In that aim, the servo-mechanism comprises two pinions born respectively by both transversal arms and mating respectively with a rack solid with the corresponding lateral rod, each of them mounted upon a shaft perpendicular to the rod and able to be made solid in rotation through a clutch with another shaft in permanent rotation, thanks to a motor, in the direction inducing the movement of each pinion towards the lower part of the corresponding rack, the servomechanism comprising also a lever controlling one or the other clutch, said lever being suspended to a piece which follows the inclination movements of the primary part and controled by another piece following the inclination movements of the secondary part, so as to control one or the other clutch when the inclination of the secondary part is higher than the inclination of the primary part towards the same side.
Other improvements could be brought to the invention, but that invention will be clearly understood through the detailed description of several embodiments, with reference to the annexed drawings.